using a jumper on the circuit-breaker box

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  #1  
Old 05-24-04, 10:54 AM
jd123
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Question using a jumper on the circuit-breaker box

One of my 120 lines went dead. So I used a jumper in the electrical box, so all the breakers would have 120 volts, without the jumper, about half my breakers are dead.

Everything is working alright so far, I don't have anything right now that runs on 240. The jumper doesn't get hot, and with everything turned on, the breakers don't throw.

The single 120 volt supply wire is aluminum and the jumper is copper wire, will they react negatively to each other? Would there be any chemical reaction?

I intend to replace the bad 120 line, but that means digging-up the yard and I don't have time right now. With the jumper, everything works. Am I safe, until I can replace the other line? thanks
 
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  #2  
Old 05-24-04, 11:23 AM
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This might be okay, or it might burn your house down in the next ten minutes. The biggest problem is the potential of a multiwire circuit. If you have two good legs of the power, they are 180 degrees out of phase and the neutral currents tend to cancel each other out. But you have made the two legs in phase. This may cause a neutral wire to overheat and start a fire. I would not want to leave it this way for more than about the next two or three minutes.

The other potential problems are that with the two legs in phase, you may overload the power company's neutral, and you have increase the voltage drop which may hasten the death of the motors in your refrigerator and washing machine.
 
  #3  
Old 05-24-04, 11:27 AM
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You also run the risk of some nasty fireworks, idepending on how you put in this jumper, if the bad leg should become energized.

Disconnect your temporary fix and solve the problem the right way.
 
  #4  
Old 05-24-04, 11:39 AM
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jd123,

What you are doing _could_ be safe, but it has substantial risk.

Question: did you put your 'jumper' in before or after the main circuit breaker? Is the panel that you are talking about a main or sub panel?

1) You have now potentially overloaded the one working line. Because of the way electrical systems are designed, the breaker does not offer absolute protection from overload. You will need to perform a load calculation and determine if the remaining line is overloaded. If you put your jumper in before the main circuit breaker, then you have effectively doubled the trip rating, which will mean that the breaker will offer essentially no protection from overload.

2) You have now potentially overloaded the neutral wire. Because many installations presume a certain amount of load balance, the neutral is often smaller than the 'hot'. With both sides of your panel bus connected to the same phase, all of the return current goes through the neutral.

3) You have now potentially overloaded the circuit breaker. Circuit breakers are only permitted to be loaded up to 80% of their trip rating on a continuous basis. By connecting things as you have, the load on one phase is roughly doubled, which could overload the circuit breaker even if it doesn't trip immediately.

4) If you somehow stuffed your 'jumper' under the main feed lugs, then you have made and extremely dangerous connection. These lugs are rated for a single wire only, and will not do a good job on two wires.

5) If you stuffed a copper and an aluminium wire into the same lug, then you are even worse off. The differential heating will cause the lug to get loose, and will cause a bad electrical connection to form.

6) Did you totally disconnect the 'blown' phase? If not, then whatever broke could slide back together, and give you a dead short on your mains.

7) If one of the wires underground has opened (are you certain that the problem is underground??), then there is presumably significant risk to the other wires. This should get checked out ASAP.

8) Did you just randomly pick a wire for your jumper? How large is it? How large is the service?

I would do the following:
1) Immediately remove the jumper.

2) Perform a load calculation to determine if your remaining hot and neutral can carry the expected load in your home. You may figure out that by removing some loads, the remaining loads can be powered without overloading the supply conductors.

3) Plan out how to properly install a temporary jumper to turn your panel into a 120V panel. You will need suitable lugs, a suitably sized jumper wire, and probably a breaker to protect the jumper wire. Using a suitably rated double pole breaker in an empty space in the panel might provide an easy way to connect the jumper to the bus.

4) After you have your temp repair plan, check back here before you install it. I'm sure others will chime in on this topic. It is unorthodox, but with care I believe it could be safe.

-Jon
 
  #5  
Old 05-24-04, 11:43 AM
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Gee Bob, good thought. The panel will probably explode in a eruption of molten metal if the missing leg of power comes back on line.
 
  #6  
Old 05-24-04, 11:50 AM
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Why didn't you just call the power company? It's free and the problem is most likely on their end.

It's not fun when you shortcircuit the hot phases on a 10,000VA power transformer. If you're luck the transformer will trip (making the electric company very unhappy), but if you're not everything in your electric panel will melt, including all service entrance cables (sure hope they are in metal conduit in this case), meter socket and meter and pretty much everything else between the transformer and your house.

This assumes that you used a suitable sized jumper of course. Otherwise that jumper will melt way before the missing hot phase is reconnected.

It's funny how many people will do something like this without knowing what they're doing.
 
  #7  
Old 05-24-04, 01:30 PM
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Originally Posted by trinitro
It's funny how many people will do something like this without knowing what they're doing.
Sometimes I just pretend it's really knowledgeable people trying to get a rise out of you guys. It's the only way I can sleep at night. Otherwise I think about the neigbors I have and realize they are probably doing the exact same thing right next to MY HOUSE.
 
  #8  
Old 05-24-04, 01:45 PM
jd123
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Thanks for the posts. I installed the jumper about a week ago. Today is the first chance I've had to get online and ask questions.

I live in the country. The utility company run the juice to the meter on the pole, when I moved out here. I ran the juice for everything else, that was 20 years ago, haven't had any problems till last week.

The first power I ran was to the well-house box, there wasn't any house here. I have three breaker boxes, pole--well-house--house, the boxes on the pole and in the well--house control both main power lines for the box in the house.

My box on the pole has two separate breakers, I turned off the breaker for the dead line. I knew which line was dead because I used a DMM on the box in the well--house. I also disconnected that dead line in the well-house and house. wrapped with electrical tape and made sure they wouldn't touch anything, like I said, the breaker at the pole is off.

The day I hooked-up the jumper in the house box, I turned on everything I could think of electrical, all the lites, floor fans, window units, computor, TV, then went out and mowed for two hours, came back in and felt of every covered wire in the house box, including the jumper, not even slightly warm. I checked again today, not even slightly warm.

I used 4/0 welding cable for the jumper, the only thing I could find in the shed. Yes, on the lugs in the house-box, the jumper and the live 120 line under one lug, the other lug only has the jumper-end.

I know I need to fix this the right way as quick as I can, it's been almost a week and the frige--well pump--everything else, seems to be working OK?

For somebody that doesn't know what they're doing, all I can say is, I guess I'm just lucky, so far? You what they say, better lucky than good.

I believe the power company responsibility ends at the meter. I believe those underground lines are mine, I put them in. thanks I can't post every day, but will keep you folks informed, if I don't get electrocuted first. thanks for talking to me.
 
  #9  
Old 05-24-04, 02:05 PM
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So are you saying that you have 220V at the pole, but not at the house? (after the underground line?)? If that's the case, then you need to replace the line. Depending on how it's wired the panel in the house is probably a subpanel now, which means you'll need to run a 4 wire feeder (2 hots, neutral and ground). You'll also probably need to have separate neutral and gound bars in the house panel. It all depends on whether you have a ground rod and the panel on the "pole".
 
  #10  
Old 05-24-04, 04:13 PM
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jd123,

It sounds to me that you are not particularly clueless on this topic, having run the wires in the first place. I do think that you have some issues with the details, and that is exactly what this discussion board is for.

I believe that you are correct; the wires that you ran from the meter to your house are your responsibility.

Your 4/0 CU is almost certainly more than enough to carry the current, unless your house in the woods is a mansion with everything electric. I am rather surprised that you could get it under the lugs in the first place, which suggests to me that your main lugs are too large, but this is _not_ certain, and depends upon the listing for the lugs involved. Putting the two wires under the lug is _generally_ a violation, but some lugs are lists for this sort of use, and if the lug is listed for multiple wires, then it is _not_ a code violation to put multiple wires on the lug.

Listed for the combination or not, I would get rid of this jumper as quickly as possible. A mix of aluminium and copper under a single screw is just badness waiting to happen. Under load the wires heat up. The copper and aluminium expand differently, and when the joint cools, you get a gap where the aluminium can oxidize. Then under load things heat up even more, and eventually the splice or junction fails.

You did the correct thing by disconnecting the broken 'hot', so the risk of a dead short though your jumper has been eliminated.

Checking the wires in the panel for heating is not really a good test. The real question is: how hot are the wires getting where they are buried in the earth and thermally insulated. Using a 'clamp on' current meter would be much better. If you measure the current with everything on, and it is below the rating of the conductor, then you are essentially fine.

Before you go digging up your conductors, I'd suggest running some sort of continuity test on the 'bad' wire. Given that you have aluminium wire, I think that there is a reasonable chance that the conductor termination failed, rather than the conductor itself.

When making connections to aluminium wire, make sure you use lugs listed for aluminium wire, use anti-oxidant on the aluminium wire, and tighten the lugs to the proper torque (not as tight a possible, but to the listed torque). Careful termination of aluminium wire is critical.

-Jon
 
  #11  
Old 05-25-04, 03:19 AM
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A further note. If you do end up changing your underground wires, I'd suggest looking at this thread on another BB:

http://electrical-contractor.net/ubb...ML/000561.html

Just a strong plug for using Cu conductors in this situation....

-Jon
 
  #12  
Old 06-04-04, 05:32 AM
jd123
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Question

I was wondering about burying a 120 line in a 17 inch deep ditch, no conduit or anything?

The other lines I ran to the well-house, I buried in pvc, it is one of those lines that is dead, there are two other lines in there that are good, so I'm not going to fool with it.

If I bury the second line in pvc, I'm going to have some weird angles at both ends, trying to dodge the other pvc line. So I'm thinking about not burying the second line in anything, just throw it in the ditch and cover it up. Any thoughts on doing it this way?

I believe I have some other 120 lines that were buried without any conduit, just as old as the other lines, no problems yet. thanks
 
  #13  
Old 06-04-04, 06:46 AM
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There are a lot of rules about buried wire. There's a table in the electrical code that covers the rules for about 40 different situations. The factors are: (1) type of cable or wire, (2) type of conduit, if any, (3) surface under which the wire is run, (4) purpose of the wire (branch or feeder), (5) presence or absense of GFCI protection, (6) size of the breaker protecting this wire, (7) voltage to ground. Feed all these factors into the table, and it will tell you the required burial depth. Or provide this information, and we'll look it up for you.

UF-B cable (and a few other types) is allowed to be direct-buried, without conduit, at least 12 inches deep (if a branch circuit protected by GFCI and a 15-amp or 20-amp breaker), under a residential landscape. Otherwise, it must be buried 24". If you need more help, let us know.
 
  #14  
Old 06-04-04, 01:53 PM
jd123
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After reading some of the posts, I thought I would check the resistance on the dead wire, as a final check, of course the wire showed [email protected]#$%^.

I had disconnected the wire at the well-house box, it was just hanging loose, I did insulate it from touching anything. Took the other end loose from the pole, it had a brownish discoloration, a little sanding took care of that. Hooked up the wire at the pole and turned on the breaker, it showed 120 volts, checked the loose end at the well, 120 volts also.

Now I'm right back where I started, except now I got a fifty foot ditch in the backyard. The original voltage problem was intermittent. I took the jumper out of the house box and everything is hooked-up correctly and working. I'm just waiting to see if that wire goes dead again.

It's a shame to let such a pretty ditch go to waste. I didn't mind the shovel work, but I didn't like swinging the pick in 90 degree weather, I'm getting too old for this.

I saw the aluminum link. Maybe my house is a little safer because, the house voltage comes from the well-house box, the well-house box cuts the pole voltage by 50 percent. 100 amp breakers on the pole, 50 amp breakers in the well-house. Everything in the house has worked fine for years and years until recently. I do see the point about aluminum wire, if I have to replace the wire, I'm going to try to use copper. thanks
 
  #15  
Old 06-04-04, 02:02 PM
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Hah, thought so.

I would suggest at this point that you go over all of the wire terminations. If the wires are going to lugs that you bolt down, I would recommend that you replace the lug where the wire was discolored. If the lugs are oversized for the wires, then replace them. Buy a bottle of 'no-al-ox', and re-terminate all of your aluminium cables. Buy or borrow a torque wrench to tighten the lugs to the recommended torque. Should be good for another 20 yrs.

-Jon
 
  #16  
Old 06-05-04, 06:11 AM
jd123
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I'm still a little suspicious of what's going on. At one time I did check for voltage on the dead wire at the pole, with everything turned on, I got 120 volts at the pole end, that is where my wire came out of the breaker, and zero volts at the well-house end.

On the box at the pole, it seems the lugs are an internal part of the breakers. I may have to replace the 100 amp breakers. Those lug-screws are rusty looking. The power company installed the box with the breakers, I'm not sure who is responsible for the breakers? I'm a little leary about taking those live lines loose from the breakers.

I may be out-of-pocket for a while, don't know when I'll get the chance to post back, so I want to thank everybody for their help. thanks
 
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